Spark plug



P. J. GRIFFIN April 23, 1929.

SPARK PLUG File-d Dec. 24, 1927 4 Patented Apr. 23, 1929. i

UNITEDSTATES PATENT OFFICE.

:PATRICK J'. GRIFFIN, OF BOSTON, MASSACHUSETTS, ASSIGNOR T0 PARAMOUNTSPABK .PLUG CORPORATION, F BOSTON, MASSACHUSETTS, A CORPORATION 0F MASSACHU- SETTS.

sraax PLUG.

This invention relates to spark plugs for internal combustion engines and has for its principal purpose the provision of an improved plug of simple and economical construction in which the elements are so disposed with'respect to the engine cylinder and in relation to the plug body that the tendency of the electrodes to become fused or fouled at the spark gap is largely obviated.

Y Other objects reside in the several novel features of construction hereafter described and defined in the appended claims, and particularly in the provision of a base chamber which is adapted to increase the cylinder space l5 whereby to afford more immediate and complete combustion of the cylinder charge.

Preferred embodiments of the invention are illustrated in the accompanying drawings, in which:

1F ig. 1 is an elevation of the improved spark u p 2 isa vertical section through the plug -of Fig. 1; Fig. 3 is a bottom view of the device; Figs. 4, 5 and 6 are detail views illustrating optional forms of a removable electrodev shown in Fig. 2; and Fig. 7 is an enlar bottom view of a modified form of the ower gasket of Fig. 2. The spark -plug body consists of a metal shell 8 having the usual exterior screw threads 9 adapted to engage the screw threads of the cylinder opening and Apreferably hav- .jing a bore 10 tapering outwardly toward the base of the plu to rovi'de a thin wall near the bottomvof t e p u and an open interior chamber of considerab e size and conse uently affording a larger space ior aecumu ation of gaseous mixture. The shell 8 also has an annular shoulder 11 adapted to force the eustomary gasket into gas-tight engagement with the outer face of the cylinder when the plug is applied in the usual manner.

'It will be observed that the tapered bore 10 extends int the shell beyondsaid shoul.

der 11; that the spark gap is positioned near the inner end of said tapered bore at the extreme u per. end of the shell chamber; and that the t readed portion of the shell is of relatively short length so that the base of the plu 'Willnot ,extend beyond the inner wall of t e cylinder. An unobstructed gas chamber which is considerably larger than has been heretofore provided is accordingly afforded by these features of construction and a more immediate and complete combustion of the cylmder charge is assured.

At the inner end of the tapered bore 10, an outwardly flaring interior annular shoulder 12 provides a seat for the ends of a removable electrode 13 which may be dropped into .the shell from its open top and which is preferably formed with shoulders 14, adjacent its ends, to ensure proper and automatic seating on said shoulder 12. The base of an insulating member 15 of porcelain or other suitable material is received within the outer or up per end of the shell and is secured by a follower nut or gland 16, gaskets 17 and 18 being provided beneath and above annular shoulders 19 and 20, respectively formed on said base. The member 15 carries a central conductor 21 preferably of brass or copper- 1ze d steel having its inner end terminating ad]ace'nt the base of member 15 which may be recessed as at 22 '(Fig. 2), and having its outer end projecting beyond the insulating member and servili as a terminal post for thc feed wire. The ase of the conductor 2 1 ma also be'recessed at 23 to provide a perip eral ridge in s ark-gap relation to the electrode 13. Thee ements of the spark plug are so arranged that, when the porcelain 15 is l tightly seated, the sparklgap between the conpreferably detachably secured within the terminal post and engages the outer end A ofthe porcelain member. A Asealing compound or paste 26is preferably employed between the conductor. `and the porcelain, including the screw-threaded rtions thereof, to ensure a gas-tight union. uch an ara ment allows the parts to `be readily assemb ed and interchanged' vwhen necessary, and p'ermits the utilization of a larger sized conductor than has been heretofore provided.

The removable electrode 13, which constitutes one of the features of this invention, may be made of nickel steel or other suitable metal vand may be formed in a variety of shapes, as indicated by Figs. 4, 5 and 6. The device of. Fig. 4 has relatively broad, Hat and substantially rectangular ends 27 and a downwardly bent central portion which is formed with a constricted neck 28; that of Fig. 5 has its ends integral with a at ring 29 and its depressed, central portion" 30 narrowand straight-sided; while the preferred form shown in perspective in Fig. 6 has lat rounded ends 31 and a straight-sided central portion 32 whose width is no greater than the ends. In each case,'the yelectrode has the spaced shoulders 13 of Fig. 2, which ensure proper, radial seating of the electrode on shoulder 12 and which also Serve to provide proper clearance between the central portion thereof and the base end of conductor 21. It is obvious however that, for some purposes of the invention, the electrode may be substantially at or may assumea shape different from those suggested herein as most suitable.

In case a free-ended electrodes/is used, such as shown in II`igs. 4 or 6, the gasket 17 which rests upon the ends of the electrodes and upon shell shoulder 12, may have diametrically disposed recesses 33 in its bottom side to accommodate said ends.

The use and electrical operation of the spark plug in an internal combustion engine, whereby the current passes through' the conductor 21 and jumps the spark gap to the electrode 13 which is grounded through contact with shell 8 to-the cylinder block (or passes in the opposite direction), is well understood. I twill be found that the spark produced by'thisplug, which occurs between the thin peripheral ridge surrounding the recess 23 and either or both edges of the electrode 13, is admirably adapted effectively to ignite the gaseous mixture accumulated within the shell chamber.

A spark plugconstructed as above described notonly aifords economies in construction andassembly and permits ready replacement of its component elements, but also eliminates to a large degree the tendency of the electrodes to fuse or to be carbonized or otherwise befoled' by the presence` offoil in the charge. Y The non-fusing feature is particularly important when the plugs are used in air-cooled engines which run at a .relatively higher temperature' than watercooled e 'nes, and Athe advantages of the improved p u are particularly adapted toensure the e cient and longcontinued operation of airplane engines in which the fusing of a spark plugis not an infrequent occurrence and often entails disastrous results.

The prevalent fusing tendency of the plugs of air-cooled engines is overcome by this invention, first, because of the provision of the large and unobstructed chamber at the base of the shell and the location of the electrodes at the top of the chamber, and second, because the electrodes are so disposed that they are positioned in the upper region of the plug and hence exterior to the enginecylinder. The first of these novel features ensures a rapid diffusion of exploded charge away from the electrodes owing tol the fact that 'the hot gases can not circulate behind the electrodes; and the second feature 'removes the electrodes from within the cylinder walls where the heat is most intense and permits them to be rapidly cooled by heat radiation at the exposed portion of the plug. These features furthermore render the porcelain insulating member less liable tocrack or break from excessive heat.

It should be understood that the details of construction herein described may be ,varied to suit particular uses without departing from the essence of this invention as defined inthe following claims.

I claim: K

1. A spark plug comprising a shell having an interior annular shoulder intermediate its ends, a removable electrode consisting of a metallic bar having its ends resting upon the upper face of said annular shoulder and having its central portion extending across the bore of the shell, said bar having shoulders between its central portion and its respective ends whereby the bar will be radially seated within the shell, agasket seated upon said shoulder and upon the ends of the electrode, a detachable insulating member secured within the upper end of the shell and having its base bearing upon said gasket, and a removable conductor passing axially through the insulating member and secured therein, the base of the conductor having spark-gap relation with the central portion of the electrode. Y v

2. A spark plug comprising a shell having an interior annular shoulder lntermediate its upper and lower ends, a substantially rigid removable ground electrode extending across the bore of the shell intermediate said annular shoulder and the lower end of the shell, said electrode having shouldered 'ends seating upon said shell shoulder, an insulating member secured within the upper end of the shell, and a conducto-r Afixed axially within the insulating member, the base of the conductor having spark-gap relation with said bar elect-rode.

3. A sparkplug comprising a shell having an interior annular shoulder intermediate its upper and lower ends, an open chamber within thel lower portion of the shell extending from said annular shoulder to the base of the shell, a substantially rigid removable bar electrode extending across the chamber, said electrode havin shouldered ends seating upon said shell s oulder, an insulating memher secured Within the upper end of the shell, and a, conductor fixed axially Within the insulating member and having its base disposed at the lowermost end of said member and in spark-gap relation with the central portion of the electrode.

Signed by me at Boston, Massachusetts, this 7th day of December, 1927.

' PATRICK J. GRIFFIN. 

